Key questions underlying this project are to what extent are currently available personalized medicine technologies being used and how does utilization vary by patient and health plan characteristics. Understanding utilization is critical to developing health care delivery models and policies. By understanding utilization patterns, we are better able to assess whether the people who would most benefit from care are indeed getting care;where there may be disparities in care;what factors influence utilization;and how interventions or policies may be used to encourage appropriate use. The Utilization Project will examine issues regarding the utilization of personalized medicine by using two topics that illustrate key issues that will be applicable to a wide range of applications of genomics in cancer care. The first, HER2 testing and trastuzumab (Herceptin) therapy, illustrates the issues involved in the utilization of a test to determine who should receive targeted therapies. The second, gene expression profiling (GEP), illustrates the issues in the utilization of a genomic diagnostic approach used for risk stratification and chemotherapy decision-making. The first topic focuses on an established guideline for the use of genomics to identify women who will benefit from a breast cancer therapy, but with complicated questions about the sensitivity, specificity, and accuracy of the diagnostic test. The second provides a scenario in which the role of the test on treatment decisions is less firmly established. The objective of the Utilization Project is to develop approaches to examining and interpreting data on the utilization of personalized medicine by using these two topics as prototypes. The Specific Aims are to: Aim 1: Evaluate the dissemination and use of personalized medicine testing in breast cancer (HER2 and GEP) as used in clinical practice by using medical record review and claims data from a large insurer (UnitedHealth). Aim 2: Assess the appropriateness of personalized-medicine based treatment decisions among women with breast cancer (trastuzumab and adjuvant chemotherapy) by using medical record review data from a large insurer and a regional group model HMO that is part of the Cancer Research Network (CRN). Aim 3: To compare the sensitivity and specificity of using claims data to identify HER2 testing, the use of trastuzumab, and GEP as compared to the "gold standard" of medical record review.